The present disclosure relates to a valve seat insert. Moreover, the present disclosure relates to a method for manufacturing a valve seat insert.
An internal combustion engine generally comprises a plurality of valves, each one of which selectively provides a fluid communication between a combustion chamber and another portion of the internal combustion engine, e.g. an intake assembly or an exhaust assembly.
A valve is generally adapted to abut a valve seat when in a closed position. The valve seat may for instance be an integral portion of a cylinder head or a separate component that is connected to the cylinder head. Such a separate component may be referred to as a valve seat insert.
U.S. Pat. No. 5,934,238 discloses a valve seat insert that comprises a layer consisting essentially of nitride for reducing adhesive and abrasive wear during use. However, there is still a need for improving internal combustion engine valve seat inserts.
It is desirable to provide a valve seat insert that has an appropriate endurance.
As such, the present disclosure relates to a valve seat insert for an internal combustion engine. A first portion of the valve seat insert is adapted to contact a cylinder head and a second portion of the valve seat insert is adapted to contact a valve. The valve seat insert has a valve seat insert volume, i.e. the entire volume of the material constituting the valve seat insert.
According to the present disclosure, a major part of the valve seat insert volume, i.e., more than 50% thereof, consists of a homogeneous material that comprises nitrides.
The valve seat insert according to the above implies a preferred endurance since a large portion of the valve seat insert volume has desired endurance properties by virtue of the presence of nitrides. Moreover, the valve seat according to the above implies that the valve seat, insert, and possibly also the cylinder head, may be machined after the valve seat insert has been inserted into the cylinder head.
As used herein, the expression “nitrides” relates to a composition of the type MN, where “M” stands for a metallic component and “N” for nitrogen. For instance, the nitrogen may have a formal oxidation state of −3.
Optionally, at least 80 vol %, alternatively at least 90 vol %, preferably least 95 vol %, more preferred at least 98 vol % of the valve seat insert consists of the homogeneous material. A homogeneous material amount at or above any one of the above limits implies an improved durability.
Optionally, the homogeneous material comprises at least 5 vol %, preferably at least 10 vol %, more preferred at least 15 vol %, of nitrides. A nitride amount at or above any one of the above limits implies an appropriately low friction and/or low risk of galling during use.
Optionally, the homogeneous material comprises at least 3 vol % of carbides. A carbide amount at or above any one of the above limit implies an appropriate wear resistance.
Optionally, the homogeneous material comprises carbides within the range of 3-6 vol %.
Optionally, the homogeneous material comprises nitrides and/or carbonitrides in the range of 12-25 vol %, preferably in the range of 14-20 vol %.
Optionally, an average size of the nitrides is within the range of 1-3 μm. An average nitride size within the above range implies a preferred machinability.
Optionally, at least 10 vol %, preferably at least 12 vol %, more preferred at least 15 vol %, of the nitrides consists of vanadium nitrides. A vanadium nitride amount at or above any one of the above limit implies an appropriate wear resistance.
Optionally, the homogeneous material consists of 0.6-1.6 weight % C, 1.5-3 weight % N, 0.2-0.6 weight % Mn, 0.3-0.7 weight % Si, 4-5 weight % Cr, 2.8-3.6 weight % Mo, 3.4-4 weight % W, 8-10 weight % V, balance Fe.
Optionally, the homogeneous material consists of 0.95-1.25 weight % C, 1.5-2.1 weight % N, 0.3-0.5 weight % Mn, 0.4-0.6 weight % Si, 4.2-4.8 weight % Cr, 3-3.4 weight % Mo, 3.5-3.9 weight % W, 8.2-8.8 weight % V, balance Fe.
A second aspect of the present disclosure relates to an internal combustion engine comprising a valve seat insert according to the first aspect of the present disclosure.
A third aspect of the present disclosure relates to a vehicle, preferably a heavy-duty vehicle i.e. a vehicle having a gross vehicle weight rating (GVWR) of 11 000 kg or more, comprising an internal combustion engine according to the second aspect of the present disclosure.
A fourth aspect of the present disclosure relates to a method for manufacturing a valve seat insert for an internal combustion engine. The method comprises:
arranging nitrided steel powder in a mould, and
densifying the nitrided steel powder.
Optionally, the nitrided steel powder has a nitrogen content of at least 0.5 weight %, preferably at least 1.0 weight %, more preferred at least 1.5 weight %.
Optionally, the nitrided steel powder consists of 0.6-1.6 weight % C, 1.5-3 weight % N, 0.2-0.6 weight % Mn, 0.3-0.7 weight % Si, 4-5 weight % Cr, 2.8-3.6 weight % Mo, 3.4-4 weight % W, 8-10 weight % V, balance Fe.
Optionally, the nitrided steel powder consists of 0.95-1.25 weight % C, 1.5-2.1 weight % N, 0.3-0.5 weight % Mn 0.4-0.6 weight % Si, 4.2-4.8 weight % Cr, 3-3.4 weight % Mo, 3.5-3.9 weight % W, 8.2-8.8 weight % V, balance Fe.
Optionally, the nitrided steel powder is densified by high velocity compaction, preferably at room temperature, to form a high velocity compacted part.
Optionally, the high velocity compacted part is sintered at a temperature exceeding 1100° C. preferably exceeding 1200° C.
Optionally, the nitrided steel powder is densified by hot isostatic pressing.
Optionally, the hot isostatic pressing is performed at a temperature exceeding 1100° C., preferably exceeding 1200° C.
Optionally, the hot isostatic pressing is performed at a pressure in the range of 100 to 350 MPa.
It should be noted that the appended drawings are not necessarily drawn to scale and that the dimensions of some features of the present invention may have been exaggerated for the sake of clarity.